Lecture 3: Introduction to Net-centric Computing CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology

Lecture 3: Introduction to Net-centric Computing

CSCI102 - Introduction to Information Technology B

ITCS905 - Fundamentals of Information Technology

Overview

This Week Background and history of networking and the

Internet Network architectures The range of specializations within net-centric

computing Networks and protocols Networked multimedia systems Distributed computing Mobile and wireless computing

Background Discussion Topics

Definitions

Describing a telecommunications system

Requirements for voice and data communications

History of telecommunications

Forces for change

Definitions

Communication “A process which allows information to

pass from a sender to one or more receivers”

“The science of transmitting information, especially symbols”

TeleAt a distance

Definitions

Telecommunications “Communications over a distance”

Definitions

Circuit: " A path over which two-way communications in

any media occurs"

Line: " A communications circuit which invariably uses a

physical wire connection"

Link: "A communications circuit is subdivided into

segments known as links ”

Definitions

Channel:A general definition would be "the part of a

communications system that connects a message source with the message sink"

In this context a channel is "a one-way communications path“

Sound

If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?

Sound

Sound depends on three thingsThere must be a vibrating source to set up

sound wavesA medium (such as air) to carry the wavesA receiver to detect them

Sound

If a tree falls in a forest far from any sound detector (such as a human ear or a microphone), does the tree's crash make any noise?

Sound

The answer, of course, depends on how sound is defined

Sound

If it is thought of as the waves that are carried by the air, the answer is yes Wherever there are sound waves there is sound

However, if sound is defined subjectively, as a sensation in the ear, for example, the answer must be no In that case sound does not exist unless there is a

receiver present to detect it

The two definitions are equally correct

Transmission Types

Analog:" An analog signal is represented in the

form of continuously varying physical quantities"

Transmission Types

Characteristics of analog signals:Frequency (constant or varying over time)Frequency range or bandwidth ( difference

between the upper and lower frequencies)Amplitude (varying over time)

Transmission Types

Analog signals are affected by a number of different types of noise and interferenceThese affect the signal clarity and include

White noise Impulse noiseSignal to noise ratioDistortionCrosstalk

Transmission Types

Amplification of analog signals is necessary to counter signal distortion and attenuation Transmission cables are likely to act as antennas

and pick up background noise This background noise is amplified as well as the

signal This noise is cumulative so the further an analog

signal travels the more amplifiers it travels through increased noise

Transmission Types

Digital:"A signal whose states are discrete

intervals apart“

Characteristics of digital signals:Discrete and discontinuousUnipolar or bipolar

1 0 1 1 1 0 0 0 1 1 0 1 1 1 0 0 0 1

Transmission Types

Any distortion that occurs while transmitting digital signals is recovered by regeneration using repeaters

Advantages of digital transmission: Lower signal error Lower noise levels Increases line capacity Less complexity Integration of voice, data and images

Transmission Types

What type of signals are sound waves?

Describing a Telecommunications

SystemA telecommunications system can be described by its key componentsTransmitterMediumReceiverCommunication network

Transmitter

Telephone, voicebox, terminal etc

Medium

Cable, air, data circuits etc

Receiver

Telephone, ear, computer etc

Requirements for Voice and Data Communications

Voice communicationsFast< 200ms delayTelco’s <70ms round-trip-delaySpeed more important than integrity

Data communicationsData integrity vs real-time

History of Telecommunications

1837 – Wheatstone and Cooke five needle telegraph

1838 - Govt declines use of telegraph1843 - First demonstration of Telegraph and

FAX in US1845 - Morse forms company1851 - 50 telegraph companies operating1856 - Western union telegraph (WUT)

established


1876 - WUT becomes the largest communications company - Alexander graham bell - patent on telephone

1876 - WUT decline to pay $100,000 for telephone1877 - Bell company formed1878 - Worlds first telephone exchange - Bell sues WUT and takes it over1885 - AT&T established interconnections between

regional telephone companies1889 – First automatic telephone system


1893/94 - Bell’s patent expires

- Independent telephone companies enter the market

1911 - Bell associated companies formed

1913 - Vacuum tube patent


1943 - Amplifiers and repeaters

1947 - Transistors

1956 - First trans-Atlantic cable laid

1957 - Launch of first satellite

1977 - Internet services provided by public carriers


1984 - Divestiture in the US1988 - Internet provides multimedia

services - Global digital interconnectivity

standards converge1993 - Formation of global consortium for

the development of global satellite and optical digital networks

What Caused the Internet ?

Sputnik I US government felt vulnerable Creation of Advanced Research Projects Agency

The Early Years

1961 - First paper on packet-switching (PS) theory1962 - J.C.R. Licklider & W. Clark, MIT: "On-Line Man Computer Communication“ (August)1962 ARPA opened a computer research program and appointed to its head John Licklider to lead it1964 - Packet-switching networks;no single outage point

The Early Years

1966/67 - plan for computer network system called ARPANET publishedIndependent teams at MIT, the National Physics Laboratory (UK) and RAND Corporation had all been working on the feasibility of wide area networksTheir best ideas were incorporated into the ARPANET design

The Early Years

Final requirement was to design a protocol to allow the computers to send and receive messages and data, known as an interface message processor (IMPs – see RFC 1)Work on this was completed in 1968In October 1969, IMPs installed in computers at both UCLA and Stanford.

The Internet – 1969

The Internet – Later that year

see RFC 4: Network Timetable

The First Login

LOG

ERROR MESSAGE:

The Early Years

UCLA students would 'login' to Stanford's computer, access its databases and try to send data

The experiment was successful and the fledgling network had come into being

The Early Years

By December 1971 ARPANET linked 23 host computers to each other

From Arpanet to Internet

1972, direct person-to-person communication that we now refer to as e-mail

host-to-host protocols (Telnet)

In October 1972 ARPANET went 'public'

TCP/IP design concepts

Crucial concept was that the system should have an 'open architecture‘

Each network should be able to work on its own, developing its own applications without restraint and requiring no modification to participate in the Internet

Within each network there would be a 'gateway', which would link it to the 'outside world'


The gateway software would retain no information about the traffic passing through

Packages would be routed through the fastest available route


The gateways between the networks would always be open route the traffic without discrimination

Operating principles would be freely available to all the networks

Going Global - 1973

First international connections to the ARPANET: university college of London (England) via NORSAR (Norway)

Ethernet

RFC 454: file transfer specification

Christmas day lockup

The Rest of the Seventies

1974 - transmission control protocol/internet protocol (TCP/IP)

1975 Operational management of Internet transferred to

DCA (now DISA) First ARPANET mailing list is created by Steve

Walker

1978 - TCP split into TCP and IP (March)

The Rest of the Seventies

1979 Computer science department research computer

network Usenet First MUD, MUD1 Internet configuration control board (ICCB) Packet radio network (PRNET) experiment starts

with DARPA funding April 12 emoticons

1980’s Expansion

The 1980’s saw a period of expansion in the internetworking community

1981BITNET, the "because it's time network"CSNET (computer science network)True names by Vernor VingeRFC 801: NCP/TCP transition plan

1980’s Expansion

1982DCA and ARPA establish the transmission

control protocol (TCP) and internet protocol (IP), as the protocol suite for ARPANET

DoD declares TCP/IP suite to be standard for DoD

1980’s Expansion

1983Cutover from Network Control Protocol

(NCP) to TCP/IP (1 January)

1984 - Domain Name System (DNS) introduced

1980’s Expansion

1986 NSFNET created (backbone speed of

56Kbps) Internet Engineering Task Force (IETF) Internet Research Task Force (IRTF)

1987Number of hosts breaks 10,000

1980’s Expansion

1988 2 November - Internet worm CERT (Computer Emergency Response

Team)DoD chooses to adopt OSI and sees use of

TCP/IP as an interim

1980’s Expansion

1989 Number of hosts breaks 100,000AARNET - Australian Academic Research

NetworkARPANET's 20th anniversary

The ‘Information Age’ Explodes

1990 ARPANET ceases to exist First remotely operated machine to be

hooked up to the Internet


1991 NSF lifts restrictions on the commercial use

of the Net (March)Wide Area Information Servers (WAIS)Gopher releasedWorld-Wide Web (WWW) releasedPGP (Pretty Good Privacy) released


1992 Internet Society (ISOC) is chartered

(January) IAB reconstituted as the Internet

Architecture Board and becomes part of the Internet Society

Number of hosts breaks 1,000,000


1993Mosaic takes the Internet by storm

WWW proliferates at a 341,634% annual growth rate of service traffic

Gopher's growth is 997%


1994 – The World discovers ‘the net’ Shopping Mall Internet Radio Spamming Governments Banking

1995 Registration of domain names is no longer free


1996 A malicious cancelbot is released on USENET

wiping out more than 25,000 messages Restrictions on Internet use around the world:

China: requires users and ISPs to register with the police Germany: cuts off access to some newsgroups carried on

Compuserve Saudi Arabia: confines Internet access to universities and

hospitals Singapore: requires political and religious content providers

to register with the state New Zealand: classifies computer disks as "publications"

that can be censored and seized


1997101,803 Name Servers in whois database

1998Network Solutions registers its 2 millionth

domain on 4 MayElectronic postal stamps


1999Technologies of the Year: E-Trade, Online

Banking, MP3 Emerging Technologies: Net-Cell Phones,

Thin Computing, Embedded Computing Viruses of the Year: Melissa (March),

ExploreZip (June)


2000RFC 2795: The Infinite Monkey Protocol Suite Hacks of the Year: RSA Security (Feb),

Apache (May), Western Union (Sep), Microsoft (Oct)

Technologies of the Year: ASP, Napster Emerging Technologies: Wireless devices,

IPv6 Viruses of the Year: Love Letter (May) Lawsuits of the Year: Napster, DeCSS


2001Viruses of the Year: Code Red (Jul), Nimda

(Sep), SirCam (Jul), BadTrans (Apr, Nov) Emerging Technologies: Grid Computing,

P2P


2002 New Top level Domains

.name (15 Jan), .coop (30 Jan), .aero (18 March) 2 September Abilene (Internet2) backbone deploys native IPv6 (5 Aug)

Internet2 now has 200 university, 60 corporate, and 40 affiliate members (2 Sep)

A distributed denial of service (DDoS) attack struck the 13 DNS root servers knocking out all but 5 (21-23 Oct). Amidst national security concerns, VeriSign hastens a planned relocation of one of its two DNS root servers

A new US law creates a kids-safe "dot-kids" domain (kids.us) to be implemented in 2003 (3 Dec)

RFC 3251: Electricity over IP


2003 Public Interest Registry (PIR) takes over as .org registry

operator on 1 Jan By giving up .org, VeriSign is able to retain control over .com

domains The first official Swiss online election takes place in Anières

(7 Jan) The SQL Slammer worm causes one of the largest and

fastest spreading DDoS attacks ever. Taking roughly 10 minutes to spread worldwide, the worm took

down 5 of the 13 DNS root servers along with tens of thousands of other servers, and impacted a multitude of systems ranging from (bank) ATM systems to air traffic control to emergency (911) systems (25 Jan)

RFC 3514: The Security Flag in the IPv4 Header (The Evil Bit)

Growth Chart

Growth Chart

Growth Chart

Growth Chart

Growth Chart

Growth Chart

Definitions

Architecture From Merriam Webster’s dictionary

“A unifying or coherent form or structure” “A set of rules or outlines needed to perform

functions according to user needs” A design

The term architecture can refer to either hardware or software, or to a combination of hardware and software

The architecture of a system always defines its broad outlines, and may define precise mechanisms as well

Definitions

Communications network architecture: “A set of design principles on the basis of

which a communications network is designed and implemented to satisfy end-user needs over a period of time”

“A set of layers and protocols”

Telecommunication Network Architectures

A telecommunications network architecture is a set of design principles used as a basis for the designing and implementation of a network

It simply describes ‘what’ will be built - it does not say ‘how’

Telecommunication Network Architectures

An architecture can be A reference model such as the open systems

interconnection (OSI) reference model Intended as a model for specific product architectures

A specific product architecture, such as that for an Intel Pentium microprocessor or for IBM's OS/390 operating system

A vocabulary for describing a protocol

An example of a network architecture is RFC 2271: an architecture for describing SNMP management frameworks

Internetworking

Internetworking is the ability to communicate across networks, with connection between networks provided at the network layer [next week] by routers or, at the data link layer, by bridges and by switches An internet is a collection of internetworked

networks The Internet is the name for the global, public

internet connecting most networks and using the TCP/IP family of protocols

Classification of Network Architecture

Open vs Closed

Extent

Ownership

Service

Quality of Service(QoS)


Open architectureAn open architecture allows the system to

be connected easily to devices and programs made by other manufacturers

Open architectures use off-the-shelf components and conform to approved standards

Closed architectureA closed architecture network is one

whose design is proprietary


ExtentThe physical space covered by the network

Pan, LAN, man, wan Internet, intranet, extranet


OwnershipPublicPrivateVirtual private networks


Service:Connection-oriented Connectionless

Quality of service(QoS)DelayReliabilityJitterThroughput


TopologyStarHierarchalMeshBusRingHybrid

Network Basics

Networks Encompass a variety of technologiesAre created and maintained by large

number of ever changing industriesMust satisfy a significant number of often

conflicting requirements

Network Basics

"No single networking technology is best for all needs“ - Comer

Universal Service to allow any two computer to communicate Regardless of

technologies they use specific networks they are directly connected to,

as long as there exists a communication path between them

References

Hobbs Timeline http://www.zakon.org/robert/internet/timeline/

RFC Indexhttp://www.rfc-editor.org/rfc-index.html

Documents

Lecture 3: Introduction to Net-centric Computing CSCI102 - Introduction to Information Technology B ITCS905 - Fundamentals of Information Technology